Aims: To conduct a case-control study of PD nested in the Agricultural Health Study cohort, in order to determine whether increased risk of PD is associated with: pesticide exposure metal exposure exposure to Nocardia asteroides, a soil microorganism lifestyle factors including diet, cigarette smoking, and alcohol and caffeine use polymorphisms in genes involved in xenobiotic metabolism, or gene-environment interactions Accomplishments: The study will be a case-control study nested within the Agricultural Health Study, a large cohort study of 82,000 licensed pesticide applicators and their spouses. It will include ~160 cases and ~480 controls. This study is the first to investigate the relationship of pesticide exposure to PD prospectively, combining direct exposure measurements with detailed life histories of pesticide use. The study will have great power to address this issue, since virtually all cohort members are exposed to pesticides, although there is considerable variability within the cohort in exposure to specific chemicals. We have developed protocols and instruments for use in the field study, and expect to begin recruiting subjects in September, 2001.